Many wireless telecommunication systems are cellular. That is, the coverage area is divided into cells, and each mobile device, or other user equipment, communicates with a base station in the cell in which it is located. In order to achieve such communication, a communication resource must be allocated to the mobile device. The available communication resources include the available communication bandwidth and the available time. Thus, in a TDMA (Time Division Multiple Access) system, the available communications channel is allocated to different users at different times, while, in a FDMA (Frequency Division Multiple Access) system, different communications frequencies are allocated to different users.
Many cellular wireless telecommunication systems use a combination of TDMA and FDMA, in that the communication resource allocated to a user comprises a particular bandwidth allocation during a specified time period.
One issue in cellular wireless telecommunication systems concerns interference. That is, where for example a mobile device is located between a base station to which it is transmitting and another base station that is also receiving signals transmitted on the same frequency, there is a danger that the signals transmitted from that mobile device will erroneously be received, and/or will cause interference at the other base station.
One way to solve this issue is to allocate the available transmission frequencies to different cells, in such a way as to reduce the probability of such interference. For example, if a transmission frequency is allocated for use by mobile devices within a particular cell of the system, then it may advantageously not be allocated for use by mobile devices within any other cell that neighbours that particular cell. This step reduces the probability that the signals transmitted from that mobile device will erroneously be received, or will cause interference at any other base station that is receiving signals on that transmission frequency.